High voltage switch with high current closing contacts

ABSTRACT

A high voltage switch for closing on high current flow has a pair of arcing contacts spaced apart at the distal end of a switch blade for engaging therebetween a graphite arcing tip prior to engagement by the switch blade of a stationary metallic contact.

[ Jan. 22, 1974 United States Patent [191 Chabala et al.

200/146 R 200/146 R 10/1972 Chabala............,............. 200/146 R 617,503 1/1899 Goldey............................ 2,989,603 6/1961 Mikos et al. 3,697,712

[ HIGH VOLTAGE SWITCH WITH HIGH CURRENT CLOSING CONTACTS [75] Inventors: Leonard V. Chabala, Ma /wood;

Primary ExaminerRobert S. Macon Attorney, Agent, or FirmKirk1and & Ellis {22 Filed: June 8,1972

21 App1.No.: 261,074

ABSTRACT Int Cl 51 H0lh 33/12 A hlgh voltage swltch for closmg on hlgh current flow 58 Field of Search 200/146 R has a P of arcing contacts spaced apart at the distal end of a switch blade for engaging therebetween a 5 graphite arcing tip prior to engagement by the switch blade of a stationary metallic contact.

I References Cited UNITED STATES PATENTS 594,656 Schwedtmann................. 200/146 R 3 Claims, 14 Drawing Figures 1 HIGH VOLTAGE SWITCH WITH HIGH CURRENT CLOSING CONTACTS This inventionis an improvement over the switch construction of Mikos et al U.S. Pat. No. 2,989,603, issued June 20, 1961.

Among the objects of this invention are: To provide for closing a switch in a circuit in which relatively high current then flows, the initial closing being accomplished with a minimum of arcing and evolution of molten metal and gas; to mount a pair of arcing contacts in spaced apart relation at the distal end of a switch blade for engaging therebetween an arcing tip mounted on a stationary contact of a switch in a'new and improved manner; to employ graphite for the arcing tip; and to support the graphite arcing tip in such manner that distributed clamping force is applied thereto.

In the drawings:

FIG. 1 is a view, in side elevation, of a switch-construction in which this invention is embodied.

FIG. 2 is a view taken generally along line 2--2 of FIG. 1 to show the construction at the upper end of the switch.

FIG. 3 is a top plan view at an enlarged scale of the upper portion of the switch along line 3--3 of FIG. 1.

FIG. 4 is a horizontal sectional view taken generally along line 44 of FIG. 1, the showing being at an enlarged scale.

FIG. 5 is a view in front elevation and at full scale of the left arcing contact member.

FIG. 6 is a view, in front elevation, of the arcing contact member shown in FIG. 5.

FIG. 7 is a horizontal sectional view taken generally along line 77 of FIG. 5.

FIG. 8 is a rear elevational view of the left arcing contact member shown in FIG. 5.

FIG. 9 is a view, in front elevation, of the right arcing contact member.

FIG. 10 is a view, in front elevation, of the arcing contact member shown in FIG. 9.

FIG. 11 is a top plan view of the arcing contact member shown in FIG. 9.

FIG. 12 is a view, in' rear elevation, of the arcing contact member shown in FIG. 9.

FIG. 13 is a full scale view, partly in side elevation and'partly in section of the arcing tip assembly.

FIG. 14 is a bottom plan view of the arcing tip assembly shown in FIG. 13.

Referring now particulary to FIG. 1 it will be observed that the reference character 10 designates, generally, a switch construction which may be employed for high voltage high current electric power circuits. For illustrative purposes it is pointed out that the switch 10 can be used on circuits operating at from 13.8 to 23 Kv in which the current may flow under fault current conditions of the order of 40,000 amperes. The switch construction 10 comprises upper and lower insulators 11 and 12 that are suitably mounted in rigid spaced relation and on which upper and lower stationary terminals 13 and 14 are mounted. A switch blade, shown generally at 15, is pivoted at 16 on the lower stationary terminal 14. The switch blade 15, as shown in FIG. 2, comprises left and right blade members 19 and 20 that are relatively widely spaced apart. The distal ends 21 and 22 of the blade members 19 and 20 are relatively narrowly spaced apart and arranged in the switch closed position to engage opposite sides of a tongue 23 that extends forwardly from the upper stationary terminal 13. A notch 24 is provided in the tongue 23, FIG. 4, for receiving a bolt 25 that extends through spiral springs 27 and 28 which serve to bias the distal ends 21 and 22 into good contact engagement with opposite sides of the tongue 23.

Mounted on the upper stationary terminal 13 and on the switch blade 15 is a load current interrupter that is indicated, generally, at 29. The details of construction and operation of the load current interrupter 29 are set forth in the patent above referred to. It will be understood that it is employed for interrupting the current flow in the circuit on movement of the switch blade 15 to the open circuit position. The present invention is concerned with the operation of the switch blade 15 when it is moved to the switch closed position and the provision of means for accommodating the flow of relatively high current, such as fault current, during such operation.

Mounted on the outer sides of the distal ends 21 and 22 of the blade members 19 and 20 are, respectively, left and right arcing contact members 31 and 32, the details of which are shown in FIGS. 5-12. Preferably the arcing contact members 31 and 32 are formed of cast leaded red brass. They have flat surfaces 33 and 34 for juxtaposition to the outer sides of the distal ends 21 and 22. They have apertures 35 and 36 through which the bolt 25 extends as shown more clearly in FIG. 4. In order to prevent pivotal movement of the arcing contact members 31 and 32 relatively to the distal ends 21 and 22 they are provided with integral detents 37 and 38 that are arranged to extend into notches at the upper ends of the distal ends 21 and 22, one of the notches 39 being shown in broken line outline in FIG. 1. The arcing contact members 31 and 32 are arranged to rock slightly when the switch blade 15 is moved to the fully closed position. For this purpose they are provided with chamfered surfaces 41 and 42.

In order to eliminate erosion of the contact surfaces of the arcing contact members 31 and 32 discs 43 and 44 of refractory arc resisting material such as a copper tungsten composition are employed. They are brazed at 45 and 46 to forwardly extending ears 47 and 48 that form integral parts of the arcing contact members 31 and 32.

Cooperating with the arcing contact members 31 and 32 is an arcing tip assembly that is indicated, generally, at 51 and shown in FIGS. 1, 2, 3, l3 and 14. The arcing tip assembly 51 extends between the spaced apart discs 43 and 44 of arc resisting material. It comprises an L- shaped bracket that is indicated, generally, at 52 and may be formed of hard drawn copper. The short arm 53 has an aperture 54 through which a bolt 55, FIG. 3, extends to mount the arcing tip assembly 51 on the upper stationary terminal 13. The long arm 56 carries an arcing tip 57 that preferably is formed of purified graphite. It is held in position by stainless steel screws 58 that extend through openings 59 in the long arm 56. The screws 58 are threaded into a stainless steel clamping plate 60 for the purpose of holding the arcing tip 57 firmly in position on the underside of the long arm 56.

It is desirable that the graphite arcing tip 57 be prevented from engaging the threads on the screws 58. This would otherwise occur when the arcing tip 57 is engaged by the arcing contact members 31 and 32 on closing the switch blade 15. Engagement with the threads would be likely to cause cracking of the graphite arcing tip 57 under these conditions. Concentration of clamping force on the graphite arcing tip is avoided through the use of the clamping plate 60.

The corners of the graphite arcing tip 57 are rounded as indicated at 64 for the purpose of facilitating the admission of the discs 43 and 44 on the arcing contact members 31 and 32. The arrangement is such that this engagement is facilitated by the rocking motion of the arcing contact members 31 and 32 caused by passage of the discs 43 and 44 along opposite sides of the arcing tip 57. The arcing contact members 31 and 32 are spread slightly apart against the biasing actions of the spiral springs 27 and 28 and the rocking motion is facilitated by the chamfered surfaces 41 and 42.

On closure of the switch blade and flow of current in the circuit, particularly flow of heavy fault current of the order of several thousands of amperes, the effects of arcing between the discs 43 and 44 of the arcing contact members 31 and 32 and the arcing tip 57 are greatly minimized. Welding of the arcing members which previously took place is eliminated and there is a minimum of display of arcing products such as molten metal and gases. Also there is a minimum of material erosion. Since nodules of molten metal are eliminated there is no interference with the movement of the switch blade 15 to the fully closed position.

We claim:

1. A switch construction for opening and closing a high voltage circuit subject to flow of relatively high current on closing comprising: a pair of switch contacts in insulated spaced relation, a switch blade pivoted to one switch contact and movable out of and into engagement with the other switch contact, a pair of arcing contact members carried in spaced apart relation by the distal end of said switch blade, said arcing contact members having chamfered surfaces contacting said switch blade whereby said arcing contact members can rock with respect to the axis of said switch blade, spring means biasing said contact members toward said switch blade so that said arcing contact members can rock freely; and an arcing tip assembly mounted on said other switch contact for engagement on closing by said arcing contact members in advance of engagement of said other switch contact by said switch blade; said arcing tip assembly including a generally L-shaped metallic bracket secured by its shorter leg to said other switch contact and extending in overlying relation to said arcing contact members, said metallic bracket including a metallic plate, clamp means, and spacer means and a graphite arcing tip carried by the longer leg of said metallic bracket and being retained against the longer leg of said metallic bracket by said metallic plate which is held against said graphite arcing tip by said clamp means, said spacer means positioned be tween the long leg and the metallic plate so that the stress applied to said graphite arcing tip by said clamp means is limited, and engageable on opposite sides by said arcing contact members said arcing contact members rocking away from said graphite arcing tip on said chamfered surfaces when said arcing contact members engage said graphite arcing tip so that stresses applied to said graphite arcing tip are reduced when said switch blade is closed.

2. Switch construction according to claim I wherein said clamp means include a pair of screws, and said spacer means include a metallic sleeve through which each screw extends.

3. Switch construction according to claim 1 wherein said arcing contact members include arcing surfaces between which and said arcing tip an arc is struck when said switch blade is closed, said arcing surfaces being formed by refractory arc resisting material. 

1. A switch construction for opening and closing a high voltage circuit subject to flow of relatively high current on closing comprising: a pair of switch contacts in insulated spaced relation, a switch blade pivoted to one switch contact and movable out of and into engagement with the other switch contact, a pair of arcing contact members carried in spaced apart relation by the distal end of said switch blade, said arcing contact members having chamfered surfaces contacting said switch blade whereby said arcing contact members can rock with respect to the axis of said switch blade, spring means biasing said contact members toward said switch blade so that said arcing contact members can rock freely; and an arcing tip assembly mounted on said other switch contact for engagement on closing by said arcing contact members in advance of engagement of said other switch contact by said switch blade; said arcing tip assembly including a generally L-shaped metallic bracket secured by its shorter leg to said other switch contact and extending in overlying relation to said arcing contact members, said metallic bracket including a metallic plate, clamp means, and spacer means and a graphite arcing tip carried by the longer leg of said metallic bracket and being retained against the longer leg of said metallic bracket by said metallic plate which is held against said graphite arcing tip by said clamp means, said spacer means positioned between the long leg and the metallic plate so that the stress applied to said graphite arcing tip by said clamp means is limited, and engageable on opposite sides by said arcing contact members said arcing contact members rocking away from said graphite arcing tip on said chamfered surfaces when said arcing contact members engage said graphite arcing tip so that stresses applied to said graphite arcing tip are reduced when said switch blade is closed.
 2. Switch construction according to claim 1 wherein said clamp means include a pair of screws, and said spacer means include a metallic sleeve through which each screw extends.
 3. Switch construction according to claim 1 wherein said arcing contact members include arcing surfaces between which and said arcing tip an arc is struck when said switch blade is closed, said arcing surfaces being formed by refractory arc resisting material. 